Hydraulic ram pumps

ABSTRACT

Hydraulic ram pump apparatus is provided, of the type including a body member (7) having a water flow passage therethrough, a waste gate (1) disposed in the passage, a delivery outlet (23) and a one-way delivery valve (10, 11) disposed in the outlet. The improvement therein lies in the waste gate (1) being pivotally mounted to the body member (7) and configured such that, in its fully open position (1a), the waste gate (1) does not significantly restrict the flow of water through said passage, in the interest of efficiency at low drive heads. The waste gate (1) is spring biased towards its open position to provide opening assistance to the waste gate (1) at low drive heads. The spring bias is such that it is at its greatest when the waste gate (1) is fully closed and is substantially zero when the waste gate is fully open.

FIELD OF THE INVENTION

This invention relates to hydraulic apparatus.

This invention has particular but not exclusive application to hydraulicram pumps, and for illustrative purposes reference will be made to suchapplication. However, it is to be understood that this invention couldbe used in other applications, such as control apparatus using thehydraulic ram principle.

The pumping of stream, lake or reservoir water for agricultural ordomestic purposes has been practiced since before recorded history. Anynumber of expressions of man's ingenuity have been applied to gettingwater from a source to a point of use. However, since there is a netenergy cost in elevating water against gravity and since the potentialenergy of the raised water is never recovered, all means of raising thewater require energy to be input. In the developed nations, the readyavailability of convenient power such as electricity and internallycombustible fuels has fostered a pumping technology substantiallydependent on such power sources. This technology is of course completelyinappropriate for use in third world or developing countries, not onlyfrom the point of view of energy supplies but also from the point ofview of keeping maintenance up to the hardware.

In areas or applications where power-dependant equipment is impossibleor undesirable to use, other means of supplying energy to the task ofpumping must be sought. Traditionally, the art of water pumping beganwith the archimedean screw. This requires manual or other power forrotation and may be powered by the wind via a windmill or by water via awaterwheel or screw. The disadvantage of the archimedean screw is asevere limitation of the obtainable head, at least while retaining theapparatus' general simplicity of construction. Other simple hardwarepowered by wind or water includes piston pumps.

Wind powered apparatus in general have the disadvantage of beingdependent upon the blowing of the wind at adequate energy flux to douseful work. Water powered apparatus are more reliable in this contextbut are often relatively complex and prone to mechanical failure andfouling. Waterwheels, screws and turbines are also very inefficient andat low heads need to be of very large size to make use of the availablepower in the water flow.

One relatively recent means of pumping utilizing the energy of a flowingstream of other water head is the use of hydraulic ram pumps. In generalterms these pumps utilize the energy of water flowing through an inlettube to close a gate across the tube. The closing of the gate creates apressure pulse upstream of the gate, which pressure pulse exceeds thelocal water pressure. The tube is provided with an outlet upstream ofthe gate and fitted with a one-way delivery valve, such that theoverpressure pulse pumps a quantity of water through the delivery valve.The delivery valve is generally air cushioned with the air supply to theair cushion being provided by a snifter valve adapted to draw air intothe tube upstream of the waste gate and thence into the delivery valve.As the overpressure pulse decays the valve closes and the gate opens toallow the bulk of the water to return to the stream or outfall as waste.The cycle is then repeated at a frequency dictated by the velocity ofthe water flow and the configuration of the gate.

Conventional hydraulic ram pumps generally do not function at heads ofless than 900 mm of water. The factors limiting low drive headperformance in conventional hydraulic ram pumps include the following:

(a) A conventional waste gate generates considerable head loss,particularly when adjusted for low drive head conditions. This head lossincreases the drive head necessary to produce satisfactory fluidvelocities in the drive pipe.

(b) The bodies of conventional hydraulic ram pumps create considerablehead loss due to a rapid change in flow direction.

(c) Conventional hydraulic ram pumps require a relatively large drivepipe "length to diameter ratio" (called L/D from here on) to operatereliably because their waste gates will not open properly with thereduced negative pressures created in hydraulic ram pumps using smallL/D's at low fluid velocities. However, small drive pipe L/D's areessential in low drive head conditions to minimise head loss in thedrive pipe.

(d) When operating at low drive heads, conventional hydraulic ram pumpstend to stop when impurities are caught in the waste gate or thedelivery valve because the negative pressures, already low due to lowfluid velocities in the pump, are reduced even further by a waste gatesealing badly. There is then insufficient negative pressure to reopenthe waste gate.

(e) To obtain useful quantities of delivered fluid when operating atvery low drive heads, a large volume of fluid must pass through thehydraulic ram pump. The cycle time of the hydraulic ram pump is alsoreduced dramatically at very low drive heads and these two factors meana large diameter drive pipe is necessary to produce a large deliveryflow per pulse. This large flow per pulse necessitates a large crosssection delivery valve to reduce friction loss, but at large deliveryheads the volume displaced by the moving delivery valve is comparable tothe volume being pumped per pulse and the pumping efficiency becomesquite small.

(f) When operating with low drive heads, hydraulic ram pumps must beinstalled very close to the down stream fluid level to maximise thedrive head available to the pump. This makes the air injecting valvevery prone to inundation when there are small changes in the streamheight. The air injecting valve is also prone to blockage due to itssmall cross section and the large positive pumping pressures which mayforce debris into the valve.

The above disadvantages are generally caused by the traditional designof the waste gate and mechanism, the delivery valve design and theperceived necessity of using a air injecting valve on the upstream sideof the waste gate.

SUMMARY OF THE INVENTION

The present invention aims to alleviate the above disadvantages and toprovide hydraulic ram pumping apparatus which will be reliable andefficient in use. It is a further object of the present invention toprovide a hydraulic ram pump which is particularly suited forapplications using head pressures at which conventional hydraulic rampumps do not operate efficiently. Other objects and advantages of thisinvention will hereinafter become apparent.

With the foregoing and other objects in view, this invention in oneaspect resides broadly in hydraulic ram pump apparatus of the typeincluding:

a body member having a water flow passage therethrough;

a waste gate disposed in said passage;

a delivery outlet; and

a one-way delivery valve disposed in said outlet, wherein said wastegate is configured such that, in its fully open position, the waste gatedoes not significantly restrict the flow of water through said passage.

Preferably, the body member comprises a substantially cylindricalhousing incorporating the waste gate and the delivery outlet and valvein a single assembly. Preferably, the inlet end of the passage isconnected to an inlet pipe which delivers the water to the assembly. Thepurpose of the inlet pipe is to set the L/D ratio discussed above, withthe optimum L/D ratio being selected as the best compromise betweenminimum head loss (small L/D ratio) and increased waste gate openingnegative pressure pulse (large L/D ratio).

The body member is preferably provided with a generally circular wastegate mounted to the body member such that the waste gate, in its fullyopen position, does not significantly restrict the flow of water throughthe passage. This is preferably achieved by providing a recess in thehousing in to which the waste gate can sit in its fully open position.In the interest of efficiency at low drive heads, the waste gate ispreferably pivotally mounted to the body member at this recess such thatthe waste gate does not significantly impede the flow of the water whenthe gate is in its fully open position. The recess is preferably in theform of a ramped recess having its deepest point at the downstream,pivoted end of the fully open waste gate. The waste gate is alsopreferably of a thickness such that the upstream edge of the waste gateis available to form a working surface for the flowing water to start topick up the waste gate from the recess. When the waste gate is picked upfrom the recess, the water flow then drives the waste gate towards theclosed position in a manner analogous to a conventional hydraulic rampump.

The body member is also preferably provided with a seat to provide animpact area for the waste gate as it closes, as well as to seal thewaste gate in its closed position. Again, it is preferable that the seatdoes not protrude significantly into the water flow path defined by thepassage through the body.

The waste gate is preferably spring biased towards its open position toprovide opening assistance to the waste gate at low drive heads.Preferably, the spring bias is such that it is at its greatest when thewaste gate is fully closed and is substantially zero when the waste gateis fully open. The large spring bias of the waste gate towards the openposition allows the waste gate to open with the very small openingnegative pressures associated with small drive heads, whilst the zerospring bias applying at the fully open position permits the same smalldrive head to pick the waste gate out of the recess and to close thesame against its seat with sufficient force to provide a positivepumping pulse.

Accordingly, in a further aspect this invention resides broadly inhydraulic ram pump apparatus of the type including:

a body member having a water flow passage therethrough;

a waste gate disposed in said passage;

a delivery outlet; and

a one-way delivery valve disposed in said outlet, wherein said wastegate is biased towards its fully open position, the said bias being atits greatest when the waste gate is fully closed and substantially zerowhen the waste gate is fully open.

The bias is preferably provided by a spring acting between the bodymember and the waste gate with it being particularly preferred to use ahelical spring about the pivot axis of the waste gate to preventunnecessary interference with the flow of water through the apparatus.

The delivery outlet is preferably disposed between the body member and adelivery pipe conveying the pumped water to a point of use or storage.Preferably, the outlet is of the type having a cushioning air chamberabove the outlet delivery valve to provide a compressible space,allowing water to pass into the outlet irrespective of the watercondition further along the delivery pipe. The delivery valve ispreferably of the type known as a disc valve and seat, wherein a discshaped member is disposed on a circular seat an retained on the seat bygravity and back pressure, with or without spring assistance. Themaximum displacement of the valve disc from its seat is preferablyadjustable in order to optimize the pumping efficiency through thevalve.

In a further aspect, this invention resides in hydraulic ram pumpapparatus of the type including:

a body member having a water flow passage therethrough;

a waste gate disposed in said passage;

a delivery outlet; and

a one-way delivery valve disposed in said outlet, wherein said one-waydelivery valve is adjustable in its extent of opening to optimizepumping efficiency of the hydraulic ram pump.

Preferably, the delivery valve is of the disc type described above andthe adjustment is provided by adjustably limiting the lift of the valvedisc off its seat during a pumping cycle. At large drive heads the valvecan be adjusted to decrease the displacement of the valve disc such thatthe volume displaced by the moving disc is less than the volume beingpumped per pulse to improve the pumping efficiency.

The delivery outlet and valve, being preferably of the air cushionedtype, must be supplied with air to replace that which inevitably passesout along a delivery pipe attached to the outlet. In the past, a airinjecting valve has been provided to provide air to the body member inthe region of the delivery valve, that is, upstream of the waste gate.However, these air injecting valves suffer from the disadvantagedescribed above at (f) in that exposure to the high positive pumpingpressures may force debris into the valve and effect a blockage.

Accordingly, in another aspect, this invention resides broadly in ahydraulic ram pump apparatus of the type including:

a body member having a water flow passage therethrough;

a waste gate disposed in said passage;

a delivery outlet positioned upstream of said waste gate;

a one-way delivery valve disposed in said outlet; and

a air injecting valve supplying cushioning air to said one-way deliveryvalve, wherein said air injecting valve is located downstream of saidwaste gate such that air is drawn through said air injecting valve andinto the body member upstream of said waste gate during the openingphase of said waste gate.

Preferably, the air injecting valve consists of a small orifice whichpasses from outside the pump body to the point in the waste fluid flowdownstream from the waste gate seat.

Since the pressure downstream of the waste gate is always lower than thepeak pressure upstream of the waste gate, the air injecting valve isnever subjected to the pumping pressures which was the primary cause ofblockage in the prior art apparatus. The air injecting valve ispreferably of a size to maintain an adequate air supply to the deliveryvalve for cushioning purposes without providing so much that theapparatus gas locks. The size of the air injecting valve is determinedby experiment in individual apparatus, if desired the air injectingvalve may be adjustable.

The downstream waste outlet of the apparatus preferably takes the formof a descending waste pipe which extends down to below the water leveldownstream of the apparatus. Such an arrangement provides for thecreation of a siphon effect assisting acceleration of the waste gate toits fully closed position and accordingly increasing the pump pulse peakpressure. A second advantage of this configuration is that the siphonconnection with the downstream water level prevents uncontrolled entryof air into the apparatus and thus prevents vapour locking of theapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that this invention may be more easily understood and put intopractical effect, reference will now be made to the accompanyingdrawings which illustrate a preferred embodiment of the invention,wherein:

FIG. 1 is a side view in vertical section of apparatus in accordancewith the present invention, and

FIG. 2 is a front view in vertical section of the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In the FIGURES, a hydraulic ram pump assembly is provided having a wastegate 1 illustrated in its fully open position 1a and illustrated in itsfully closed position 1b. The waste gate 1 is pivotally mounted on ashaft 2 located transverse to and out of the direct line of the waterflow. The waste gate 1 is biased towards its fully open position byspring 4 coaxial with the shaft 2. The waste gate 1 is adapted to sealin its fully closed position against annular seal ring 5. The water issupplied to the apparatus via feed pipe 6 attached to the inlet side ofhousing 7. The waste gate 1 in its fully open position rests in recess7a in the lower portion of the housing 7 , which recess alsoaccommodates the shaft 2 and the spring 4. The waste side of the housing7 is terminated by an annular seal housing 9 adapted to retain the seal5 as well as to mount waste outlet pipe 8. The seal housing 9, seal 5and waste pipe 8 are of a diameter similar to that of the inlet pipe 6such that the flow of water is not significantly impeded. The waste pipe8 is curved down to the downstream water level to provide a siphon toassist the water hammer action of the apparatus to open and close thewaste gate 1.

The upper portion of the housing 7 upstream of the waste gate 1 isprovided with a delivery outlet comprising apertures in the housing 7.The apertures are closed by a delivery valve comprised of a valve disc10 adapted to seal against seal 11. The displacement of the valve disc10 on the pump stroke is limited by stop 12 which is adjustable viaselectable spacers 13. The delivery valve is housed in housing extension15 formed integrally with the housing 7. The housing extension 15defines an air space 15a which provides elastic cushioning of the pump.The valve housing 15 is provided with a delivery port 23 to which adelivery pipe can be attached. The cushioning air for the valve issupplied by air injecting valve 14 located downstream of the wastegate 1. The air injecting valve 14 consists of a small orifice whichpasses from outside the pump body to the point in the waste fluid flowdownstream from the waste gate seat.

The shaft 2 is mounted to the housing 7 via shaft sleeve 20. The shaftsleeve 20 also provides a mounting point for the spring 4 at 16. Theeffective spring tension is controlled by rotation of the shaft 2 andsleeve 20 assembly relative to the waste gate 1 extension to the shaft2. This relative rotation is effected by rotation of control lever 17attached to the shaft 2. Start and stop control of the assembly isprovided by start/stop lever 19 acting on sleeve 19a which is providewith gate opening lug 22. A gate closing lug 21 is provided on the wastegate 1. The position of the lever 19 is retained as desired by lock nut18.

The open waste gate 1(a) is nearly in balance in the position shown withthe combined forces of gate 1(a) buoyancy and spring 4 torsion nearlybalancing the gravitational force acting on the gate 1(a). In thisposition the open gate 1(a) rests lightly against gate stop 3 andcreates very little head loss. As the fluid velocity passing the leadingedge of gate 1(a) from drive pipe 6 reaches a point where the pressureand viscous forces acting on the gate 1(a) overcome all other forcesacting on the gate 1(a), the gate 1(a) begins to close. (the sum ofspring 4 torsion, buoyancy and gravitational forces acting on the gateis defined as the gate opening force and hereinafter called F_(o)).

The gate 1(a) rotates clockwise about gate pivot shaft 2 and as the gate1(a,b) projects further into the fluid flow the increasing pressure andviscous forces more than cope with the increasing F_(o) and the gate1(a,b) quickly accelerates up to the velocity of the water.

When the waste gate 1(a,b) reaches the closed position, the gate openingforce F_(o) has increased significantly because the spring 4 which wasacting to close the gate 1(b) when the gate 1(a) was open, is now actingwith the negative pressure pulse to open the gate 1(b), and thegravitational and buoyancy forces acting to open the gate 1(b) havedropped to almost zero.

This large value of gate opening force F_(o) when the gate 1(b) isclosed enables the gate 1(b) to swing open with only very small negativepressures associated with operating the pump at small L/D's and/orsealing problems due to debris caught between the gate 1(b) and thewaste gate seat 5.

Waste tube 8 carries the fluid which has passed through the pump wasteoutlet 9 in a large radius to the downstream fluid level. The waste tube8 is either immersed under the down stream fluid or has its open endtilted back. This traps fluid in the waste tube 8 and prevents gasentering the pump body 7.

The waste tube 8 also acts as a siphon and applies most of the pressuredifference between the upstream and downstream fluid level across thedrive pipe 6. Consequently, the hydraulic ram pump may be mounted ashigh as the upstream fluid level and away from potential flooding.

The delivery valve disc 10 deals against the valve seat 11 and isconstrained in its movement by valve stop 12. The volume of fluiddisplaced by valve disc 10 when it opens is determined by the distancebetween the top of the valve disc 10 and the bottom of the valve stop12. This distance may be adjusted by changing the thickness of thespacers 13 to optimise the delivery efficiency of the hydraulic ram pumpat different delivery heads.

Air injecting valve 14 injects gas into the downstream side of the wastegate seat 5 because there is always negative pressure inside the pumpwaste outlet 9.

This negative pressure is normally small due to the siphon effect of thewaste tube 8 and momentarily large due to the negative water hammereffect when the waste gate 1(b) closes.

When the waste gate 1(a,b) opens after a pumping cycle, the reverse flowof water through the pump waste outlet 9 carries some of the injectedgas into the roof of the pump body 7 where it is subsequently carriedinto the air chamber 15 during the following pumping cycle.

One end of spring 4 is rigidly connected to control lever 17 by springclamp 16 which clamps spring 4 to the pivot shaft 2 through shaft sleeve20. The position of control lever 17 and consequently, spring clamp 16determines the maximum value of F_(o). The force F_(o) acting on thegate 1(a,b) may be adjusted by moving control lever 17 to suit specificpumping conditions. When control lever 17 is correctly adjusted, locknut 18 may be tightened to prevent control lever 17 from moving.

Because all moving parts of the low drive head hydraulic ram pump arenot directly accessible, it is necessary to provide a means of openingand closing the gate 1(a,b) from outside the pump body 7.

This is necessary to manually pump air out of the pump body 7 if thehydraulic ram pump has been stopped for any length of time.

When lock nut 18 is loose, rotation of start/stop lever 19 past thepoint where it contacts gate opening lug 21 causes the gate 1(a,b) toopen. If start/stop lever 19 is rotated in the opposite direction pastthe point where it contacts gate closing lug 22, the gate 1(a,b) may beforced to close.

It will of course be realised that while the above has been given by wayof illustrative example of this invention, all such and othermodifications and variations thereto as would be apparent to personsskilled in the art are deemed to fall within the broad scope and ambitof this invention as defined in the claims appendant hereto.

I claim:
 1. A hydraulic ram pump apparatus comprising:a body memberhaving a water flow passage therethrough; a waste gate pivotally mountedin said passage and being movable between an open position wherein watermay flow past said waste gate and a closed position wherein said wastegate substantially closes said flow passage; a delivery outlet having anon-return valve therein and located upstream of said waste gate, saiddelivery outlet having an air chamber having air compressed by thepassage of water delivered to said air chamber through said non-returnvalve, said air being supplied through an air injection valve locateddownstream of said waste gate and into said body member upstream of saidwaste gate during the opening of said waste gate; and a waste wateroutlet downstream of said waste gate; and gate biased away from theclosed position, the bias being greatest when the waste gate is closedand the bias being substantially non-existent when said waste gate isopen.
 2. The hydraulic ram pump of claim 1 wherein said air injectionvalve comprises an orifice communicating with the fluid flow toatmosphere, said orifice providing a valve action due to the relativevelocities of air and water.